| Gram stain | <microbiology, procedure> A method of staining bacteria using a violet stain. The gram staining characteristics (denoted as positive or negative) can assist in the identification of the offending bacteria. A heat fixed bacterial smear is stained with crystal violet (methyl violet), treated with 3% iodine/potassium iodide solution, washed with alcohol and counterstained. The method differentiates bacteria into two main classes, gram-positive and gram-negative. Certain bacteria, notably mycobacteria, that have walls with high lipid content show acid-fast staining the stain resists decolouration in strong acid. (27 Sep 1997) |
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| Weigert-Gram stain | <technique> A stain for bacteria in tissues in which sections are stained in alum-haematoxylin, then in eosin, aniline methyl violet, and Lugol's solution. (05 Mar 2000) |
| half-a-gram stain | <technique> A lab technique used to detect the presence of members from the bacterial family Legionellaceae in samples of sputum. (09 Oct 1997) |
| Stirling's modification of Gram's stain | <technique> A stable aniline-crystal violet stain. (05 Mar 2000) |
| relative molecular mass | The sum of the atomic weight's of all the atoms constituting a molecule; the mass of a molecule relative to the mass of a standard atom, now 12C (taken as 12.000). Relative molecular mass (Mr) is the mass relative to the dalton and has no units. See: atomic weight. Synonym: molecular mass, molecular weight ratio, relative molecular mass. (05 Mar 2000) |
| cloning, molecular | The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells. (12 Dec 1998) |
| models, molecular | Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. (12 Dec 1998) |
| molecular | <chemistry> Of, pertaining to or composed of molecules: a very small mass of matter. (18 Nov 1997) |
| molecular behaviour | <psychology> Behaviour described in small response units rather than larger ones; a specific response. Compare: molar behaviour. (05 Mar 2000) |
| molecular biology | <study> The study of the biochemistry of cells, it is closely linked to cell biology, in particular the biochemistry of DNA and cogeners. (16 Dec 1997) |
| molecular biophysics | Biophysics concerned with membrane processes, conformational and configurational properties of macromolecules, bioelectrical phenomena, etc. (05 Mar 2000) |
| molecular chaperones | A family of cellular proteins that mediate the correct assembly or disassembly of other polypeptides, and in some cases their assembly into oligomeric structures, but which are not components of those final structures. It is believed that chaperone proteins assist polypeptides to self-assemble by inhibiting alternative assembly pathways that produce nonfunctional structures. Some classes of molecular chaperones are the nucleoplasmins, the chaperonins, the heat-shock proteins 70, and the heat-shock proteins 90. (12 Dec 1998) |
| molecular clock | This term has two separate uses. 1. <molecular biology> The rate of fixation of mutations in DNA and thus times the rate of genetic diversification. 2. <cell biology> A biological system capable of maintaining up a timing rhythm or pulse. All such clocks are thought to be entrained by a natural oscillator such as the diurnal rhythm. (18 Nov 1997) |
| molecular cloning | <molecular biology> The biological amplification of a specific DNA sequence through mitotic division of a host cell into which it has been transformed or transfected. (09 Oct 1997) |
| molecular conformation | The characteristic three-dimensional shape of a molecule. (12 Dec 1998) |